L-theanine, a natural constituent in tea, and its effect on ...

Tea is the most widely consumed beverage in the world after water. It is renowned for its rich content of flavonoid antioxidants, but what many may not know is that it also contains L-theanine, a unique amino acid that can influence brain function in humans. Research using electroencephalograph (EEG) studies has illustrated its direct impact on the brain (Juneja et al. Trends in Food Science & Tech ;10;199-204). L-theanine has been found to significantly enhance activity in the alpha frequency band, indicating a relaxing effect on the mind that does not promote drowsiness. However, this effect has predominantly been observed at doses exceeding those typically found in a standard cup of black tea (approx. 20mg). The objective of current studies was to verify this effect at more practical dietary levels. EEG responses were recorded in healthy young volunteers at baseline and at intervals of 45, 60, 75, 90, and 105 minutes following the ingestion of 50mg of L-theanine (n=16) versus a placebo (n=19). While participants rested with their eyes shut during the EEG measurement, the results revealed a notable increase in alpha activity in the L-theanine group compared to the placebo (p+0.05). A separate study further confirmed these findings in participants engaged in passive activities, suggesting that L-theanine, at realistic dietary levels, may considerably enhance mental alertness and arousal states. Moreover, alpha activity is crucial for various attention-related aspects, and further investigations are underway to understand the implications of L-theanine on attention processes.

You will get efficient and thoughtful service from Witspower.

Effects of L-Theanine on Cognitive Function in Middle-Aged Adults

Abstract

L-theanine (γ-glutamylethylamide), an amino acid found in green tea, has demonstrated its potential to modify certain cognitive functions by alleviating stress, boosting mood, and promoting sound sleep. Nevertheless, the specific cognitive areas where L-theanine is effective remain ambiguous. This study sought to clarify the positive cognitive effects of L-theanine consumption. A double-blind, randomized, placebo-controlled study was performed focusing on Japanese individuals aged 50 to 69 years, with a Mini Mental State Examination-Japanese score of 24 or above. The Cognitrax assessment was utilized to evaluate cognitive function before the intervention, after a single dose of L-theanine, and after 12 weeks of consistent intake. Findings showed that a single dose of L-theanine reduced response time in attention tasks (Stroop test, Part 1), increased the accuracy in working memory tasks (4-Part continuous performance test, Part 4), and decreased omission errors. The results indicated that L-theanine could significantly enhance attention, thus supporting working memory and executive functioning.

Keywords: attention, brain function, Cognitrax, executive function, green tea amino acid, working memory

Introduction

L-theanine is a nonproteinogenic amino acid found in green tea and mushrooms. Among various tea varieties in Japan, gyokuro and matcha boast higher levels of L-theanine compared to sencha. Studies indicate that L-theanine impacts brain functions effectively. Animal studies have shown that L-theanine enhances behavioral output under stress, mitigates learning capabilities deterioration under social stress, and addresses memory impairments.

Epidemiological studies, such as Nakajima and Tsurugaya, have suggested that green tea may aid in reducing cognitive decline associated with aging. Concurrently, the Hisayama study has highlighted a concerning uptrend in Alzheimer's disease prevalence. As dementia remains a critical global challenge, finding preventive measures is essential.

Green tea comprises various components affecting cognitive functions, including caffeine, L-theanine, and catechin. While caffeine provides immediate cognitive enhancement post-consumption, previous research implicated that regular consumption of matcha tea may also contribute to improved attention. However, this observation pointed to factors beyond caffeine influence, implying that consistent tea intake could play a significant role.

Additionally, L-theanine's neuroprotective properties have been documented, demonstrating its ability to inhibit delayed neuronal death following transient ischemia, decrease excitotoxicity by regulating glutamate release, and promote neurogenesis; thus potentially mitigating cognitive decline. Yet, the effects of L-theanine on cognitive functions in humans harbor many uncertainties that this study aims to address.

Materials and Methods

This research was conducted at the Tokyo Skytree Station Medical Clinic, Tokyo, Japan, with approval from the Nihonbashi Egawa Clinic Research Ethics Committee. This study adhered to the Declaration of Helsinki guidelines from August to December . The study was registered with the University Hospital Medical Information Network.

Test Food

L-theanine (trade name: Suntheanine; Taiyo Kagaku Co., Ltd., Mie, Japan) served as the test food. The product had a purity level of '98% and was encapsulated in No. 1 porcine gelatin capsules. A placebo was fabricated in identical capsules, utilizing corn starch as an excipient. Each L-theanine capsule contained 100.6'mg of the amino acid and was manufactured at Sunsho Pharmaceutical Co., Ltd. (Shizuoka, Japan).

Subjects

A total of 69 Japanese individuals were recruited, certified healthy through hematological and biochemical tests, and recognizing cognitive function decline. Individuals scoring less than 24 on the Mini Mental State Examination-Japanese were enrolled, while those with food allergies or on medications affecting cognitive performance were excluded.

The subjects volunteered for the study after receiving complete informational briefings about the study.

Study Design

A double-blind, randomized placebo-controlled parallel group study was enacted. The primary endpoints involved assessments from MMSE-J and Cognitrax, while secondary endpoints focused on amyloid levels along with brain-derived neurotrophic factor (BDNF) levels. Randomized group assignments were executed based on age, sex, and MMSE-J score through a stratified schema. Participants consumed one capsule of either placebo or L-theanine daily for a period of 12 weeks, typically after breakfast. Those who skipped breakfast ingested the test food in the morning. Subjects maintained freedom in consuming other polyphenol-containing beverages but were advised against health foods or supplements impacting cognitive functions.

Evaluation Items

Evaluation metrics consisted of a thorough medical interview, physical measurements, and test scores which involved cognitive assessments like MMSE-J and Cognitrax, conducted at baseline, after single-dose intake, and at the 12th-week mark. Safety assessment included blood tests at baseline and after 12 weeks.

Blood Biomarkers

A comprehensive analysis rendered no significant differences between placebo and L-theanine groups.

Discussion

This study explored how L-theanine affects cognitive capabilities through the Cognitrax test. Our aim was to determine if regular consumption of L-theanine over 12 weeks could enhance attentional functions or identify which cognitive processes a single dose would influence.

Each cup of green tea generally contains around 25mg of L-theanine. Interestingly, Kuriyama et al. have indicated that individuals consuming green tea demonstrate less cognitive dysfunction. Previous research underscored that a 50.3mg dose of L-theanine led to performance improvements in attention, consistent with the 100.6mg found in this study. Results suggest that L-theanine not only decreases response time in attention tasks but also enhances performance in working memory through increased focus and attentional resources.

Notably, while caffeine and L-theanine present differing effects on neural activity, they are both constituents of green tea. Existing literature highlights the synergistic effects of their combined consumption on cognition, mood, and attention. Our findings reaffirm the singular influence of L-theanine in enhancing working memory performance, likely aided by prior attentional improvements. It remains to be explored whether these combined effects stem from the interplay between catechins, caffeine, and L-theanine, necessitating further investigation into the individual and collective impacts of these tea components.

To learn more about L-Theanine for Cognitive, contact us today and secure an expert consultation!

Contact us to discuss your requirements of L-Theanine for Nootropic. Our experienced sales team can help you identify the options that best suit your needs.